Mixing Game Content

  It is not possible to mix game content (Use weapons/materials/models/maps from different Source games) if you wish to run on all players’ machines that are running. This is because there is no guarantee that the person downloading your map has both installed the games that use your materials installed.
  For example, you can not use the AK-47 Weapon in a Half-life single player mod because there is no way of ensuring that the people who play your mod for Half-Life 2 also have Counter-Strike: Source also installed and fully updated. Players who lack both Games' respective files would get an error, and be unable to play your mod.